Patent GB-190420970-A (GB)
Title: Improvements in and connected with Braking or Stopping Devices for Electric Motors
Inventor: HULTQVIST ARTHUR
Filed: 1904-09-29
Granted: 1905-09-07
Abstract: 20,970. Hultqvist, A. Sept. 29. Motors, controlling.-A special switch is employed to shortcircuit a motor armature to prod u c e a braking effect. One form of switch is shown in Fig. 1. A rotary contact-drum 1, mounted on a shaft 2 journalled in a case 3, carries two sets of contactbars separated by a flange 22 of insulating-material. A spring 4 is fixed to the drum 1, and is capable of turning the drum through half a revolution. The drum may be turned by a handle 5 to put the spring 4 in tension, and is fixed in position by a pawl 171 engaging with a notched disc 8 on the shaft 2. The pawl is carried by a spring 6 which also carries an armature 7. Electromagnets with coils 25, 26 and cores 23, 24 are arranged to release the drum by attracting the armature 7 and to blow out any sparks at the contacts. The connections are shown in Fig. 4. A local circuit with battery 27, press-button 28, and relay 29 may be used to effect the release of the contact-drum 1. The contact-plates 9, 10, 11, 12, 13,14 are shown in the running position. The current flows from the main 31 through the resistance 32, spring arm 16, contact-plate 9, arm 15, motor armature 35, and armature 30 of the relay 29 to the main 38. A shunt circuit is provided through the arm 18, contacts 11, 14, arm 21, field coil 40 of the motor, arm 17, contacts 10, 13, and arm to the armature 30 of the relay. When the button 28 is pressed, the local circuit is completed, and the armature of the relay is attracted. This completes the circuit of the coils 25, 26 of the electromagnets, and the contact-drum makes half a revolution. The armature 35 is then shortcircuited as shown in Fig. 5. The switch may also be arranged to introduce suitable resistances in the armature circuit, or may connect electromagnetic brakes in the circuit. The push-buttons 28 may be replaced by an ordinary circuit-closer 47, Fig. 6, actuated by a cord 46 arranged as a safety-device along a shaft 43 driven by an electromotor. When the circuit-closer 47 operates, the motor armature is short-circuited as before. The switch 48 may be operated by hand to produce the same effect. The relay may be connected across the main wires, or may be omitted and the magnetizing-coils of the switch connected in circuit with the pressbutton. In a modification, the rotary contactdrum is replaced by contact-knives held by a suitable detent, the disengagement of which causes the contact-knives to fall over a series of resistance studs. The detent is released by the core of a solenoid. Another form, suitable for connection to a three-phase motor, is shown in Fig. 9. The contact-lever 62 is released by the core 71 of the solenoid 70, and is thrown, by the spring 69, over the resistance studs 72, 73, 74, 75 and 76,77, 78, 79, each set being connected to one of the phases of the motor but reversed in relation to the contacts 67, 68. A dash-pot 86 is used to check the fall of the lever 62. The connections are shown in Fig. 11, the supply end being indicated at 87 and the motor at 93. The contacts 65, 66 are fixed to the lever 62, Fig. 9. The line-wire 88 is connected to the motor, and the other two lines 89, 90 are connected to the pole-plates 96, 97 and 98, 99 of the switch 100. When the lever 62 falls, the motor connections are changed and the machine runs as in an asynchronous generator until the end position is reached, and the motor is disconnected from the source of current.